The complete or partial detachment of ligaments, tendons or other soft tissues from their associated bones within the body is a relatively common injury, particularly among athletes. Such injuries generally result from excessive stresses being placed on these soft tissues. For example, a tissue-detaching injury may occur as the result of an accident such as a fall, overexertion during a work-related activity, during the course of an athletic event, or in any one of many other situations and/or activities.
In the case of a partial detachment, commonly referred to under the general term “sprain,” the injury will frequently heal itself, if given sufficient time, and if care is taken not to expose the injury to any undue or extraordinary stress during the healing process. If, however, the ligament or tendon is completely detached from its associated bone or bones, or if it is severed as the result of a traumatic injury, partial or permanent disability may result. Fortunately, a number of surgical techniques exist for re-attaching such detached tissues and/or completely replacing severely damaged tissues.
One such technique involves the re-attachment of the detached tissue using traditional attachment devices such as metal staples, sutures, and cancellous bone screws. Such “traditional” attachment devices have also been used to attach tendon or ligament substitutes (often formed of autogenous tissue harvested from elsewhere in the body) to the desired bone or bones. Another technique is described in detail in U.S. Pat. No. 4,950,270 entitled “Cannulated Self-Tapping Bone Screw” issued Aug. 21, 1990 to Bowman et al., which is incorporated herein by reference in its entirety. In this technique, an anterior cruciate ligament in a human knee, for example, is replaced and/or repaired by forming bone tunnels through the tibia and/or femur at the points of normal attachment of the anterior cruciate ligament. A ligament graft, with a bone plug on at least one of its ends, is sized to fit within the bone tunnels. Suture is then attached to the outer end of each bone plug, and thereafter passed through the femoral and/or tibial bone tunnels. The femoral plug and/or the tibial plug is/are then inserted into the appropriate bone tunnel behind the suture. Subsequently, the suture is drawn tight (simultaneously in opposite directions, in cases where bone plugs are to be located in both a femoral bone tunnel and a tibial bone tunnel). This procedure positions the bone plug (or plugs) in the desired location, and imparts the desired degree of tension to the ligament or ligament substitute. Finally, while holding the bone plugs in position, a bone screw is inserted between each bone plug and the side wall of its associated bone tunnel so as to securely lock the bone plug in position using a tight interference fit.
With the advancement of anterior cruciate ligament surgery from the open reconstructions to arthroscopic-endoscopic reconstructions, surgeons are faced with a number of choices concerning graft fixation, both at the femur and the tibia. These ligament fixation devices have been introduced to the orthopaedic community, often with mechanical studies that bear little relevance to the actual demands of postsurgical rehabilitation and return to sports mechanics. Thus, it can be difficult for the surgeon to determine those fixation devices that will prove the most reliable during early healing stages.
A number of principles have been established in the last decade concerning anterior cruciate ligament (ACL) surgery, which when adhered to usually result in an excellent outcome. Anatomic placement, no femoral condylar notch impingement, early range of motion, and strong, rigid fixation are but a few of these important principles. Some current devices, however, cannot withstand repeated cycling motions without loss of fixation strength. Moreover, depending on the fixation point of the graft within the bone tunnel, the graft can wear against the bone eventually resulting in tearing or breakage of the graft.
Accordingly, there is a need for an improved tissue fixation device that provides a strong, rigid fixation, and that avoids the risk of tearing or breakage of the graft.